The Tissue Culture Core Laboratory of the Diabetes Center has been in operation since 1975, and provides expertise and materials to those funded investigators whose research relates to diabetes and other areas of metabolism and growth control. The purpose of the Tissue Culture Core Laboratory is four-fold: 1) to provide media, sera, and related tissue culture supplies in a cost-effective manner to Diabetes Center members, and to provide quality control on media, sera, and other biologicals supplied by the core laboratory; 2) to maintain widely-used cell culture lines on a routine basis (both as frozen stocks and ongoing cultures), and to aid investigators in establishing specialized cell lines from primary sources; 3) to provide technical expertise in a wide variety of specialized techniques related to cell culture, assays on cells and cell components, karyology, cell synchrony, and genetic approaches (including introduction of cloned genes into mammalian cells by a variety of methods); 4) to maintain costly equipment needed jointly by several investigators in the Diabetes Centers, so that these equipment items do not have to be purchase individually by investigators. In the last five years, we have expanded the number of Core Laboratory users to an average of 27 Diabetes Center members, and have greatly expanded the number of specialized assays and techniques available through the Core Laboratory (including the preparation, maintenance, and assay of hybridomas, and the introduction of recombinant DNA molecules into cultured cells). The long-range goals of the Core Laboratory are to facilitate any experiments being performed by Diabetes Center members that involve cultured cells, including establishment of permanent cell lines, isolation of various cell organelles, and assays for hormone-responsive enzymes and other biological molecules.